LED light sources are rapidly becoming competitive with fluorescent lamps with respect to luminous efficacy. Known LED light sources typically require rewiring the fixture so that line voltage is directly connected to the LED lamp connectors, bypassing the ballast. LED light sources have been developed that connect the replacement LED lamp to the output of the ballast. Accordingly, it has become more difficult to replace existing fluorescent lamps, since it may not be readily apparent if a fixture has been rewired to bypass the ballast, or is still wired through the ballast without at least partial disassembly of the light fixture.